(a) Field of the Invention
This invention generally relates to a clutch mechanism for engaging a drive shaft to a drive sprocket. More particularly, but not by way of limitation, to a clutch mechanism which allows disengagement of a drive pulley, hub, and the like, through a sliding action.
(b) Discussion of Known Art
Various clutch mechanisms have been developed, each including physical features that offer advantages for the particular application. Known clutch mechanisms fixedly attach components of the clutch mechanism directly to the drive shaft. The attachment of the clutch components to the drive shaft is typically carried out by providing a flattened section on the drive shaft. One of the clutch's components is then fastened to the drive shaft by means of a set-screw, key, or the like. For example, it is known that a friction plate and fly-wheel combination may be attached to the drive shaft by way of a key. The key or other attachment transmits torque, primarily as a shear force, from the drive shaft on through to the clutch components. The friction plate and fly wheel will then cooperate with an opposing friction plate to transmit power to a driven shaft. Thus, known clutch mechanisms achieve the selectable engagement result by adding components which fixedly connect to the drive shaft, and thus require additional components that complicate the mounting and actuation of the clutch mechanism. These additional components make proper installation of the clutch mechanism difficult. Difficulties associated with the installation in turn lead to operational difficulties and power transfer inefficiencies.
This approach to the construction of clutch mechanisms has significant disadvantages in that the attachment of a clutch component to the drive shaft requires the provision and alignment of a mating element in the driven shaft. The mounting of mating elements on a pair of shafts involves precision machining or skilled labor for proper alignment and operation. Additionally, the stacking of several components in series can lead to serious problems with mounting space, necessitating the use of parallel gearing or mounting mechanisms to reduce the overall length of the installation. For example, in the mechanisms discussed in U.S. Pat. No. 5,557,887 to Fellows et al. Illustrates the use of a parallel shaft attached to reducing gears which eventually lead to an output shaft.
A known clutch or selectively connectable coupling is shown in FIG. 3 of U.S. Pat. No. 5,222,327 to Fellows et al ("Fellows '327"). The mechanism shown in the Fellows '327 patent includes a a sliding gear with a splined aperture that is supported on a mating splined drive shaft. The gear can then be engaged or disengaged from succeeding drive train components by a movement of the gear over the splined shaft.
Other known publications teach mechanisms that are particularly useful in the selective engagement of drive mechanisms for overhead garage doors. These publications include U.S. Pat. No. 5,222,403 to Angelini et al., U.S. Pat. No. 4,472,910 to Iha, U.S. Pat. No. 4,131,830 to Lee et al., U.S. Pat. No. 3,722,141 to Miller, and U.S. Pat. No. 3,220,718 to Wikkerink. A review of these publications reveals a need for a simple selective engagement mechanism for the drive mechanism on systems such as garage door drive systems. Importantly, there remains a need for a selective engagement mechanism that can be attached to the drive system of a wide variety of drive mechanisms, the engagement mechanism cooperating with the output shaft of drive mechanism.
Furthermore, there remains a need for simple selective engagement mechanism that can be activated by a variety of linear, rotary, or leverage devices.
Still further, there remains a need for a selective engagement or clutch mechanism that eliminates components, such as a drive shaft attachment, while still maintaining the function of selective engagement.